[SCSI] qla4xxx: added new function qla4xxx_relogin_all_devices

Move relogin to all devices code from do_dpc to new
fuction qla4xxx_relogin_all_devices()

Signed-off-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>